Latham : Stimulation of Sterigmatocvstis 343 



pette to be analyzed for acid and sugar. The remainder was then 

 inoculated In bulk with spores in the method described and doses 

 of 50 c.c. run from the pipette into each culture dish. Last of 

 all the iron, a mere trace, was added. 



The crop was reaped when the controls showed a full fruited 

 surface. The felts were thrown on weighed filters, washed thor- 

 oughly with boiling water, dried in hot air at yo^-80^ C, cooled 

 in a desiccator and the dry weight ascertained. The filtrate made 

 up to 250 c.c. was analyzed, as recorded, for oxalic acid, or sugar^ 

 or both. Determinations for oxalic acid in the filtrate from the 

 Sterigmatocystis'^ were made at once. Ten cubic centimeters of 

 the solution were titrated against standardized NaOH. The total 

 acidity, less the acidity at the time of setting up (that of the stock 

 solution), gave the correct amount of acid produced during" 

 growth. 



A measured quantity of the filtrate, generally 100 c.c, was 

 next inverted by boiling with 0.5 c.c. of 5N HCl and the invert 

 sugar estimated by the Fehling test. When asparagine was pres- 

 ent, extra care was taken. A cubic centimeter or 1.5 ex, of 

 acid was used for inversion and the time of boiling extended, 

 water being added if necessary. Asparagine, by virtue of its 

 amide groups, will reduce a copper solution and invalidate a test 

 for sugar in its presence. Hard boiling with HCl serves to de- 

 stroy the molecule with the production oi NH^Cl, which does not 

 interfere with the analysis. The Fehling solution was kept in two 

 portions. The stock CuSO^ contained 69.28 gms. per liter; the 

 alkaline tartrate, 100 gms. of NaOH and 350 gms. of KNaC^H^O 

 per liter. Standardization was made against accurately freshly pre- 

 pared i per cent, dextrose. For each analysis 5 c.c. of each stock 

 solution and 40 c.c. of H^O were used. Calculations were made 

 on the basis that under such conditions 0.5 gm. of invert sugar 

 reduces 97 c.c, of the Fehling solution. f 



The fruiting of the control cultures, as mentioned, determined 

 the reaping of the crop. The period of growth varied with the 

 temperature. Near its optimum of 34^ C, Sterigmatocystis was 



* Wehmer, Entstehung und physiologische Bedeutung der Oxalsaure im Stoff- 



wechsel einiger Pilze. Bot. Zeit. 49 : 189I. 

 I Sutton. Volumetric Analysis. Ed. 1904. 



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